Investigate how the resistance changes in a wire of different lengths.

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Introduction

AndrewThe Resistance in a Wire16th November

Lightstone

Variables: - There are many variables for this experiment: the material of wire, the voltage, the width of the wire, and the length of the wire.

Factors to observe: - You could see how the temperature changes and how the resistance changes due to the variables.

Aim: - to investigate how the resistance changes in a wire of different lengths. This means my variable will be the length and factor to observe will be the resistance. In order to make it a fair test, all possible variables (except the length) must be kept constant. If I change the material of the wire half way through, its structure might be different to the one used previously i.e. there might be more particles for the electrons to bump into, so there would be a sudden jump in resistance between the two. If I accidentally changed the voltage, by moving it either higher or lower, their would be more or less current passing through, that that of the rest of the experiment, so it wouldn’t be a fair test of resistance and there would be large jumps in my measurements.

Prediction: - Once my results have been collected, the graph will look like this:

Resistance (ohms)

Length (cm)

The wire with ruler, will be connected into the circuit with crocodile clips. The clips will be at 0 and 10 cm on the ruler. I will turn the voltage up to 2V and record the Amps in my table. I will then move the crocodile clips apart another ten centimetres so 1 is on 0 and another is on 20. Again I will record the amps and volts. I will do this all the way up to 80 cm – making sure not to touch the wire, because by my predictions it should be quite hot. Once the graph is filled, I will go about finding the resistance with the formula V/I = volts/current. I will record the resistance in the table.

Preliminary work: - Before the actual experiment, I carried out a dummy experiment in order to get to know how to set up the circuit and also to see what problems could arise through doing the main experiment. I recorded the lengths, volts and amps and worked out the resistance. My table was as follows: -

As I was doing the experiment, I looked back at my results constantly, and constantly, I found I had put the wrong thing due to misreading the ammeter.

I could not do anything about the flicking amp and volt meter, but I could about making the wire tighter, and checking it was perfectly straight, and also by making sure I put the main part of the crocodile clip on the number of the length I intend to measure.

As well as this, too make the experiment a lot more accurate, would be, instead of taking measurements every 10cm, to take measurements every 5 cm. This would fill in the gaps between the points so I could make a better line of best fit. Also I could continue my measurements up to the area of about 200 – 250 cm, so I could see any extreme temperatures the heat and length have on the resistance.

Although my graph is not perfect, it gives the basis for me to say that it proves my prediction to be right, and any alterations to the experiment, will not have such an effect on the graph, that it will change it. I think my graph is relatively reliable, because even with any changes to the method, the graph will still remain in near enough the same shape.

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